The present invention relates to improvements in plastic bags and method of making plastic bags formed in a continuous bag chain where adjacent bags are joined by an interconnection and wherein the bags can be separated either manually or by a machine operation during an automatic filling procedure.
The bags which are involved are thin plastic film bags which have sides and a bottom edge and a the upper end have a reclosable zipper lock structure. The zipper lock structure constitutes a set of interlocking rib and groove profiles. The lock structure is closable and the bag is closed by applying an opposed closure pressure progressively along the length of the profile elements. The lock structure and the bag is opened when the profiles are separated by either drawings them apart, such as by pulling flaps which extend above the profiles laterally or by longitudinal movement of one profile relative to another in such a manner that the profiles snap apart. Reclosable bags of the type described are disclosed, for example, in U.S. Pat. Nos. re 28,969, 3,338,284 and Re 29,208.
In the manufacture of bags of the above type, they are typically made by the plastic being continuously extruded from a circular die to form an endless profile tube. However, the bags can be made from a folded flat film with interlocking profiles adjacent either end with said profiles either attached integrally or separately attached. In other words, the profiles can be formed integrally with the material of the bag or may be on strips which are then secured to the bag material. In the tubular form, the mating interlocking profiles are formed on the inner surface of the tube. The profiles are joined when the plastic has cooled sufficiently to eliminate distortion of the plastic. Subsequently, individual bags are formed by cross-seals at spaced intervals to form a seam at each of the side edges of each of the bags with the bags being simultaneously cut from the tube at said seam.
In one commercially advantageous form, the bags are manufactured and are stored to be sold and shipped to the user who opens, fills and recloses the individual bags. These bags may be stacked in boxes, but in one preferred form, the bags are interconnected to each other in strip or chain form with individual bags torn off of the supply strip. This form of chain of bags is advantageously utilized in automatic filling and handling machines, and one arrangement for utilizing such a chain of bags is disclosed in the copending application, Ser. No. 429,617, now U.S. Pat. No. 4,490,959 issued Jan. 1, 1985 where automatic machinery has been devised for feeding, opening, and reclosing the reclosable bags. Such mechanism utilizes a series of interconnected bags drawing them along a travel path through work stations of the machine. At one section of the machine, the individual bags are removed from the supply chain by being forcibly torn from the chain. Whether torn from the chain or otherwise disconnected, a relatively high speed production operation can occur by pulling the chain of bags from a supply source, either a roll or a box and having individual bags disconnected from the chain as they are handled by the machine.
A significant feature of providing such a chain of bags is that the formation of the chain or interconnection of the bag be done simply without interfering with the manufacturing operation and without adversely affecting the strength and appearance of the bag. Also, whether the bags are forcibly torn from each other, or the interconnecting means is broken or separated by other arrangements as will be described herein, the bags must be separated without damage to them, and also separated rapidly and easily without slowing the high speed operation of the filling and closing machine.
It is accordingly an object of the present invention to provide an improved method and bag chain wherein individual bags can be supplied in a chain and removed from the chain readily and easily and uniformly without endangering the integrity of the bags.
A still further object of the invention is to provide an improved bag chain structure wherein the bags are reliably and simply attached to each other and are easily and readily removed from the chain.
A further object of the invention is to provide an improved bag chain structure wherein the ease of separation of the bags can be controlled by the structure.
A still further object of the invention is to provide an improved structure for the attachment of bags to each other to form a continuous chain wherein the structure serves to accurately align the adjacent bags to each other maintaining the interlocking rib and groove elements and the top and bottom edges in alignment.
A feature of one form of the invention is to manufacture bags sequentially and provide a removable strip along one or both edges wherein the strip can be separated to sequentially release the bags such as by tearing the strip from the edge.
Another feature of the invention is accordance with another form, is to provide a frangible strip attached to the bags wherein the strip is laminated to the bag material in a surface-to-surface engagement so that it is reinforced over the area of attachment but frangible in the area between the bags thus permitting a strip of uniform weight to be used. The strip can be formed of clear material which does not interfere with the appearance of the bag or can be formed of a decorative material which contributes to the structure and function and appearance of the bags.
Other objects, advantages and features, as well as equivalent methods and structures, will become more apparent from the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawings, in which: